Implantable Devices and Methods for Measuring Intraocular, Subconjunctival or Subdermal Pressure and/or Analyte Concentration

ABSTRACT

Methods, apparatus and systems for measuring pressure and/or for quantitative or qualitative measurement of analytes within the eye or elsewhere in the body. Optical pressure sensors and/or optical analyte sensors are implanted in the body and light is cast from an extracorporeal light source, though the cornea, conjunctiva or dermis, and onto a reflective element located within each pressure sensor or analyte sensor. The position or configuration of each sensor&#39;s reflective element varies with pressure or analyte concentration. Thus, the reflectance spectra of light reflected by the sensors&#39; reflective elements will vary with changes in pressure or changes in analyte concentration. A spectrometer or other suitable instrument is used to process and analyze the reflectance spectra of the reflected light, thereby obtaining an indication of pressure or analyte concentration adjacent to the sensor(s). The wavelength of the interrogating beam of light may vary to control out potential interference or inaccuracies in the system.

RELATED APPLICATIONS

This application is a division of copending U.S. patent application Ser.No. 13/185,277 filed Jul. 18, 2011, which is a division of copendingU.S. patent application Ser. No. 10/754,479 filed Jan. 9, 2004 nowabandoned, which claims the benefit of U.S. Provisional ApplicationsSer. No. 60/439,307 filed Jan. 9, 2003 and 60/439,308 filed Jan. 9,2003, the entire disclosure of each such prior application beingexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION Measurement of Intraocular Pressure

The term “glaucoma” encompasses a group of diseases, which causeprogressive damage to the optic nerve and resultant optical fielddefects, vision loss and, in some cases, blindness. Typically, glaucomais frequently, but not always, accompanied by abnormally highintraocular pressure.

There are three basic types of glaucoma—primary, secondary andcongenital. The most common type of glaucoma is primary glaucoma. Casesof primary glaucoma can be classified as either open angle or closedangle.

Secondary glaucoma occurs as a complication of a variety of otherconditions, such as injury, inflammation, vascular disease and diabetes.

Congenital glaucoma is elevated eye pressure present at birth due to adevelopmental defect in the eye's drainage mechanism.

Glaucoma is the third most common cause of blindness in the UnitedStates. Whether it is an increase in the intraocular pressure thatcauses damage to the retina or an increased susceptibility to damagethat may result in an increase in intraocular pressure, titrating theintraocular pressure with careful monitoring is the mainstay oftreatment and constitutes an important component in the overall clinicalmanagement of the disease.

The etiology of vision loss in glaucoma patients may be due, at least inpart, to compression of the vasculature of the retina and optic nerve asa result of increased intraocular pressure. Indeed, it is generallyaccepted that controlling intraocular pressure through the use of drugsand/or surgery markedly reduces glaucomatous progression innormal-tension glaucoma and decreasing intraocular pressure virtuallyhalts it in primary open-angle glaucoma. Furthermore, it is generallyacknowledged that lowering intraocular pressure in glaucoma patients canprevent or lessen the irreversible glaucoma-associated destruction ofoptic nerve fibers and the resultant irreversible vision loss.

Thus, irrespective of the particular type of glaucoma a patient suffersfrom, it is typically desirable to obtain periodic measurements ofintraocular pressure in order to assess the clinical progression of thedisease and/or the efficacy of the treatments being administered. Also,because early diagnosis is important in effectively treating glaucoma,it is also desirable to periodically measure intraocular pressure inpatients who do not presently suffer from glaucoma but who may be atrisk to contract one of the various types of glaucoma.

Today, intraocular pressure is commonly measured by indirect methods(e.g., pressing a strain gage against the cornea and measuring the depthof corneal depression) or by non-contact methods (e,g., expelling a puffof air against the outer surface of the cornea and measuring the depthof corneal depression). As convenient as these measurements may be, theyare inherently inaccurate, mainly because of the error imparted by thevarying mechanical properties of the cornea. It has been shown that suchindirect intraocular pressure measurements are dependent upon, amongother factors, corneal thickness, curvature and rigidity. These factorscan vary greatly from individual to individual, and thus gross errors inintraocular pressure estimation are common. These errors can easilyresult in the misdiagnosis of a glaucomatous or non-glaucomatous state.Moreover, with the advent of corneal refractive surgery, 1.8 million ofwhich were performed in the U.S. last year, measurement of intraocularpressure via indirect methods through the cornea is even more inaccuratesecondary to the biomechanical alterations of the cornea caused bysurgery. Thus there is a great national and international need todevelop a more accurate direct intraocular pressure sensor.

In the past, there have been numerous attempts to construct an accurate,small and safe intraocular pressure sensor. Among the devices proposedwere direct cannulation of the anterior chamber of the eye coupled to anextraocular direct pressure monitor, and telemetric units usingpiezoresistive and acousto-optic elements. Such devices would beimplanted in the anterior chamber either as free-standing units, orincorporated as parts of plastic intraocular lenses. The telemetricmachines would transfer intraocular pressure readings to externalmonitoring devices non-invasively through the intact cornea. Althoughthose previously proposed telemetric devices offer potential advantagesover their invasive counterparts and the current indirect cornealdevices, they still suffer many drawbacks including bulk, need forelectrical power and unacceptable signal-to-noise ratios.

Recently, intracavity pressure sensors (e.g. brain and intravascularspace) based upon the Fabry-Perot interferometer, in which two parallel,minimally separated, partially reflecting surfaces form an opticalreflecting cavity, have been proposed. If one of the parallel surfacesis a pressure-sensitive diaphragm, changes in external pressure cause achange in the depth of the optical reflecting cavity, which in turnalters optical cavity reflectance spectra. Because brain andintravascular elements are optically opaque, current use requires asingle wavelength light-emitting diode physically coupled to an inputand read-out fiber optic. Alternatively, for the purposes of thiscurrent invention, we recognize that the anterior chamber and cornea areoptically clear. Thus the input optical wavelengths and reflected outputcan be detected externally through intact and optically clear anteriorchamber and cornea media after intraocular implantation of such achip-based pressure sensor, either as an independent device or as partof an intraocular lens. In this case, because we are not restricted bythe spectral bandpass of an optical fiber, almost any light source,including various LEDs, lasers or white light emitters (filtered andunfiltered) may be used. Moreover, currently available sensors shouldprove small enough for practical intraocular implantation. Theadvantages of direct intraocular pressure sensing, no need forelectrical power, non-invasive external monitoring, compact chip-baseddevice and optical sensing with high signal-to-noise ratio have beenrealized in this invention.

Measurement of Intraocular, Subconjunctival or Subdermal AnalyteConcentrations

In clinical medicine, it is sometimes desirable to measure theconcentration of glucose and/or other analytes within the eye or atother locations within the body, in order to diagnose and/or monitorvarious conditions including, but not limited to, metabolic or endocrinedisorders such as such as diabetes mellitus. Various methods includingdirect analytical sampling and various forms of spectroscopy have beenproposed in the past. Frequent direct invasive sampling, especially fromthe intraocular and intravascular spaces, has obvious problems.Non-invasive spectroscopic monitoring through skin and intravascularelements has sensitivity and specificity problems associated with boththe optical opacity and turbidity of these media and the narrow (butoften overlapping) spectroscopic chemical bands of each individualanalyte.

Recently biomembranes permeable to specific analytes (e.g. glucose) havebeen developed. Sensors for these selected compounds usually incorporatedirect spectroscopic detection or transduced increased pressureassociated with increasing concentrations of the chemical. Such methodseither involve invasive sampling of the sample chamber orelectrical-powered piezoresistive signal transduction and read-out, allserious drawbacks of the proposed methods.

There remains a need in the art for the development of new devices andmethods for measurement of intraocular pressure and/or measurement ofintraocular, subconjunctival or subdermal analyte concentration.

SUMMARY OF THE INVENTION

The present invention provides implantable devices, systems and methodsfor measuring intraocular pressure and/or intraocular, subconjunctivalor subdermal anaylte concentration(s).

In accordance with the invention, there is provided an intraocularpressure measuring system that comprises a) an inplantable opticalpressure sensor sized for implantation within the eye, said opticalpressure sensor comprising an optical reflecting element which variesrelative to changes in intraocular pressure, b) a light source useableto pass light through the cornea of the eye such that the light willstrike and be reflected by the optical reflecting element and c) areceiver/processor which receives light which has reflected from theoptical reflecting element and processes such reflected light so as toobtain an indication of intraocular pressure. The optical pressuresensor may comprise a Fabry-Perot interferometer. Such optical pressuresensor may be constructed for implantation as stand-alone device or itmay be attached to or otherwise associated with a support (e.g., asupport member, housing, substrate or other structure) that holds theoptical pressure sensor in a substantially fixed (e.g., substantiallystationary) position within the eye. Such support may hold the opticalpressure sensor at a desired location within the eye where intraocularpressure may be sensed (e.g., within the anterior chamber, posteriorchamber or lens capsule). In some embodiments, the support may comprisean intraocular lens assembly having an optic portion and a hapticportion. The optical pressure sensor may be attached to (e.g., mountedon, embedded in or otherwise connected to) the optic portion and/or thehaptic portion of such intraocular lens assembly. The optic portion mayor may not be configured to perform a refractive vision correctingfunction. In other embodiments, the support may be in the form of atubular shunt that is implantable in the eye to facilitate drainage ofthe drain aqueous humor in glaucoma patients and the optical pressuresensor may be attached to a portion of the shunt that protrudes into theanterior chamber of the eye. In other embodiments, the support maycomprise an implantable prosthetic lens that is useable to replace anative ophthalmic lens that has been removed from the patient's eye(e.g., a cataract that has been surgically removed) and the opticalpressure sensor may be attached to such prosthetic lens. The support maybe configured to perform other secondary functions or it may beconfigured to function solely as a support for the optical pressuresensor without performing any secondary function(s). The light sourcemay comprise an LED or other light emitting apparatus that emits lightof a desired wavelength (e.g., white light). The optical pressure sensormay be positioned at a location within the eye whereby light from thelight source will pass inwardly through the cornea of the patient's eye,strike and be reflected by the reflective element of the opticalpressure sensor. The reflected light will then pass outwardly throughthe cornea and will be received and processed by the receiver/processor.Because the optical pressure sensor moves in response to changes inintraocular pressure, the wavelength of the reflected light also changesin accordance with such changes in intraocular pressure. Thus, thereceiver may be a lens, mirror or any other single or multiple lightreceiving or light channeling apparatus. The processor may be aspectrometer or any other apparatus that measures or detects changes inthe wavelength of the reflected light received by the receiver. Thereceiver/processor may comprise an integrated, single assembly thatincorporates both the receiver and processor. Alternatively, thereceiver/processor may comprise a receiver that is separate from and notphysically connected to the processor.

Further in accordance with the invention, there is provided a system forfor intraocular, subconjunctival or subdermal determination of one ormore analytes (e.g., chemical substances). Such analyte determinationsystem generally comprises a) an optical analyte sensor sized forintraocular, subconjunctival or subdermal implantation, said opticalsensor comprising an optical reflecting element which varies relative tochanges in the amount or concentration of the analyte, b) a light sourceuseable to pass light through the cornea, conjunctiva or skin such thatthe light will strike and be reflected by the optical reflecting elementof the optical sensor and c) a receiver/processor which receives lightthat has reflected from the optical reflecting element and processessuch reflected light to obtain a qualitative or quantitativedetermination of the analyte. The analyte may be a substance that occursnaturally within the body (e.g., glucose, certain enzymes, hormones,etc.) or a substance that has accumulated in or entered the body (e.g.,certain drugs or toxins of exogenous origin). As used herein the terms“subconjunctival” and “subdermal” refer to locations beneath at leastthe upper surface of the conjunctiva or skin and, thus, are to beconstrued to include locations within the conjunctiva or skin as well aslocations that are entirely beneath the conjunctiva or skin. The opticalreflective element of the optical analyte sensor may move in response tochanges in the osmolar pressure, osmolarity and/or osmolality(collectively “osmolar changes”) of a body fluid that result fromchanges in the concentration of the analyte within that body fluid. Inthis regard, the optical analyte sensor may comprise a closed chamberthat is at least partially closed by a permeable or, more typically, asemipermeable membrane. As osmolar changes occur in the body fluidadjacent to the semipermeable membrane, fluid will diffuse into or outof the chamber, through the semipermeable membrane. Such diffusion offluid into or out of the chamber will result in upward or downwardmovement of the reflective member in response to the osmolar changes inthe adjacent body fluid. This results in changes in the wavelength ofthe light reflected by the reflective member. Such changes in wavelengthare detected by the receiver/processor and the presence or concentrationof the analyte in that body fluid is determined on the basis of suchchanges in wavelength of the reflected light. Thus, as in theabove-described pressure sensor, the receiver may be a lens, mirror orany other single or multiple light-receiving or light-channelingapparatus. The processor may be a spectrometer or any other apparatusthat measures or detects changes in the wavelength of the reflectedlight received by the receiver. The receiver/processor may comprise anintegrated, single assembly that incorporates both the receiver andprocessor. Alternatively, the receiver/processor may comprise a receiverthat is separate from and not physically connected to the processor. Theoptical analyte sensor may be constructed for implantation asstand-alone device or it may be attached to or otherwise associated witha support (e.g., a support member, housing, substrate or otherstructure) that holds the optical analyte sensor in a substantiallyfixed (e.g., substantially stationary) intraocular, subconjunctival orsubdermal location. Any of the support types described above withrespect to the optical pressure sensor may also be used with thisoptical analyte sensor. Additionally, various other types of functionalsupports may be used in subconjunctival or subdermal applications of thedevice (e.g., the optical analyte sensor may be mounted on a drugdelivery implant or other medical device that is implanted within orbeneath the skin).

Still further in accordance with the invention, the optical pressuresensor and the optical analyte sensor may be used in combination. Inthis regard, the optical pressure sensor and the optical analyte sensormay be mounted on a common support, of the types described herein. Insuch embodiments wherein the optical pressure sensor and the opticalanalyte sensor are used in combination, a single light source orseparate light sources, may be used to cast light on the opticalpressure sensor and the optical analyte sensor. In embodiments where asingle light source is used, such single light source may be adjustableto vary the direction, wavelength and/or other characteristics of the ofthe light beam that emanates from the light source, thereby facilitatingits use for both applications. Also, a single receiver/processor orseparate receiver processors may be used to receive and process thelight reflected from the optical pressure sensor and optical analytesensor. In embodiments where a single receiver/processor is used, suchsingle receiver/processor may be adjustable to vary the direction fromwhich the reflected light is received and/or the particularcharacteristic(s) of the reflected light that are processed by theprocessor.

Still further in accordance with the invention, there are providedmethods for measuring or determining intraocular pressure and/orintraocular, subdermal or subconjunctival analyte concentration usingthe devices and systems summarized above.

Further aspects, elements, embodiments and details of the invention willbe apparent to those of skill in the art upon reading of the detaileddescription and examples provided herebelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial, cross-sectional view of a human eye having animplantable pressure sensor device of the present invention implantedwithin the anterior chamber of the eye.

FIG. 2 is a schematic diagram of a pressure sensing system of thepresent invention, including the implantable pressure sensor device ofFIG. 1 in combination with an extracorporeallly positionedmicroscope/light source and an extracorporeallly positionedspectrophotometer.

FIG. 3A is a cross sectional view of the implantable pressure sensordevice of FIG. 1 with its diaphragm positioned in response to a lowintraocular pressure.

FIG. 3B is a cross sectional view of the implantable pressure sensordevice of FIG. 1 with its diaphragm positioned in response to a highintraocular pressure.

FIGS. 4-7 are previously published graphs (excerpted from Wolthius etal.) showing the linearity and accuracy of Fabry-Perot interferometersof the type used in the present invention. Specifically; FIG. 4 showsreflecting cavity depth for light emitted at 820, 850 and 880 nm; FIG. 5shows sensor reflectance and dichroic ratio plotted with respect tooptical cavity depth; FIG. 6 shows absolute pressure vs. dicrotic ratio;FIG. 7 also shows absolute pressure vs. dicrotic ratio.

FIG. 8 is a schematic diagram of a analyte sensing system of the presentinvention comprising an implantable analyte sensor implanted within theanterior chamber of a human eye in combination with an extracorporealmicroscope/light source and an extracorporeal spectrometer.

FIG. 9A is a cross sectional view of the implantable analyte sensordevice of FIG. 8 with its diaphragm positioned in response to a highconcentration of analyte in the aqueous humor of the eye.

FIG. 9B is a cross sectional view of the implantable analyte sensordevice of FIG. 8 with its diaphragm positioned in response to a lowconcentration of analyte in the aqueous humor of the eye.

FIG. 10 shows an embodiment of the present invention wherein an opticalpressure sensor and optical analyte sensor are attached to a commonsupport.

DETAILED DESCRIPTION AND EXAMPLES

Recently intracavity pressure sensors (e.g. brain and intravascularspace) based upon the Fabry-Perot interferometer, in which two parallel,minimally separated, partially reflecting surfaces form an opticalreflecting cavity, have been proposed. If one of the parallel surfacesis a pressure-sensitive diaphragm, changes in external pressure cause achange in the depth of the optical reflecting cavity, which in turnalters optical cavity reflectance spectra. Because brain andintravascular elements are optically opaque, current use requires that asingle wavelength light-emitting diode be physically coupled to an inputand read-out fiber optic. In contrast, for the purposes of the currentinvention, the cornea and conjunctiva are optically clear and that thedermis poses no optical obstruction to various defined wavelengths oflight (or the dermis may be treated with one of more chemical agents tominimize the light scattering properties of the dermis). Thus the inputoptical wavelengths and reflected output from the optical pressuresensors and optical analyte sensors of the present invention can bedetected externally through intact corneal, conjunctival and dermalmedia and will not be restricted by the spectral bandpass of an opticalfiber and because of the optical clarity of these structures. Also, inthe systems of the present invention, almost any light source, includingvarious LEDs, lasers or white light emitters (filtered and unfiltered)may be used (in the case of skin, the dermis must be transparent to thewavelengths). The advantages of direct pressure sensing and/or analytedetermination systems of the present invention include; the lack of anyneed for electrical power to the implant, the capability of non-invasiveexternal monitoring, and a comparatively high signal-to-noise ratio havebeen realized in this invention.

As described in detail herebelow, FIGS. 1-7 relate to one particularnon-limiting example of an intraocular pressure sensing system of thepresent invention, FIGS. 8-9 b relate to one particular non-limitingexample of an intraocular analyte determining system of the presentinvention and FIG. 10 relates to one particular non-limiting example ofan intraocular pressure sensing and analyte determining system of thepresent invention. Several of these figures depict anatomical structuresof the human eye. Such anatomical structures are labeled as follows:

AC Anterior Chamber C Cornea I Iris P Pupil L Native Lens

EXAMPLE 1 Intraocular Pressure Sensing System

An intraocular pressure sensing system of the present invention is shownin FIGS. 1-3 b. As may be seen in FIG. 1, an optical pressure sensor 10is mounted on a support 11. This support 11 comprises a haptic 14 and anoptic 12, in the nature of a typical phakic intraocular lens adapted forimplantation within the anterior chamber AC of the eye. In theembodiment shown, the optical pressure sensor 10 is attached to one edgeof the optic 12, but it is to be appreciated that the optical pressuresensor could also be attached to the optic 12 and/or haptic 14 at otherlocations or in other ways. The optic may or may not provide somerefractive vision correction in addition to performing the function of asupport 11 for the optical pressure sensor 10. On example of a 2-piecephakic intraocular lens that may be used to form the support 11 is theKelman Duet Implant manufactured by TEKIA, Inc., Irvine, Calif.

The support 11 holds the optical pressure sensor 10 at a substantiallyfixed (e.g., substantially stationary) position within the anteriorchamber AC such that the pressure sensor 10 will sense changes in theaqueous humor that fills the anterior chamber. Such pressure of theaqueous humor typically becomes abnormally high in patients who sufferfrom glaucoma and, thus, this embodiment of the invention is useable tomonitor disease progression and/or treatment efficacy in glaucomapatients.

FIGS. 3a and 3b show details of the intraocular pressure sensor 10. Asshown, this intraocular pressure sensor 10 comprises a translucent body16 (or alternatively an opaque body having a translucent window formedtherein) with an optical reflecting cavity 18 formed at one end thereof.A flexible diaphragm 20 forms the bottom wall of such cavity 18. Areflective surface 22 is formed on the upper surface of the diaphragm20. A separate reflective surface may also be formed on the wall of thecavity 18 that is opposed to the reflective surface 22 of the diaphragm20. The optical pressure sensor 10 is positioned in the anterior chamberAC such that the underside of the outer surface of the diaphragm 20 isin contact with the aqueous humor that fills the anterior chamber AC.When the intraocular pressure is normal, the force exerted on thediaphragm 20 by the aqueous humor will allow the diaphragm 20 tosubstantially remain in a first position, as shown in FIG. 3A. However,as the intraocular pressure increases, the diaphragm 20 willprogressively move upwardly, as shown in FIG. 3B.

The optical pressure sensor 10 may be a miniaturized Fabry-Perotinterferometer in which two parallel, minimally separated, partiallyreflecting surfaces form an optical reflecting cavity which iscommercially available as Model 20 and Model 60, from RJC Enterprises,Woodinville, Wash. The size of the optical pressure sensor is about 300μm×300 μm with about 200 μm depth. One of the parallel surfaces 22 is asurface of the pressure-sensitive diaphragm 20 that changes positionwith changes in external pressure. This results in a change in the depthof the optical reflecting cavity 18 and a resultant change in thereflectance spectra. Thus, the changes in the reflectance spectracorrelate with changes in depth of the reflecting cavity 18 and, thus,also correlates to changes in the pressure of the aqueous humor in theother side of the diaphragm 20.

FIG. 2 illustrates the manner in which intraocular pressure is read fromthe implanted optical pressure sensor 10. A light source 30 ispositioned in front of the patient's eye. A beam of light is cast fromthe light source 30, through the cornea C of the eye, though thetranslucent body (or window) of the sensor 10 and upon the reflectivesurface 22 of the diaphragm 20. This light is then reflected from thereflective surface 22, outwardly through the cornea C and is received bya receiver 32 such as a mirror, lens, waveguide or other light directingmember. The reflected light is directed by the receiver 32 to aprocessor 34, such as a spectrometer, which then processes the reflectedlight in a manner that determines a parameter of the reflected lightthat is dependent upon the depth of the reflecting cavity 18 and, thus,can be used to calculate the pressure of the fluid exerted against thepressure sensitive diaphragm 20.

The processor 34 may be a reflectance spectrum analyzer that measuresthe difference in reflected light emanating from the optical sensor 10at different wavelengths. The reflectance of the optical sensor 10 isnot only dependent on the depth of the reflecting cavity 18 cavity andthus on the pressure, but is also dependent on the wavelength of thelight that is transmitted against the reflecting surface 22 of thediaphragm 20 from the light source 30. In this regard, FIG. 4 (excerptedfrom Wolthius et al.) shows the relationship between the depth of thereflecting cavity 18 and reflectance determined by the processor 34 whenthe light source 30 emits light at wavelengths of 820, 850 and 880 nm.By determining the ratio of the reflectance of different wavelengths,the signal to noise ratio can be improved and the linearity range can beextended, as demonstrated in FIG. 5 and the following equation:

Δ=π(λc−λc′)/2ω where w is the spectral width of the light source,λA_(c), λ_(c′) are the wavelengths of the two probing light sources

K=(1−R′)2/2R′ where R′ is the mean reflectance of the surfaces

Ratio=1/2+2 /π [(1−K) sin Δ′/2K−(1−K) cos Δ′]

FIG. 5 shows the total sensor reflectance (measured photocurrent) andthe output from dichroic ratio signal analysis(dichroic ratio) plottedwith respect to optical cavity depth (absolute pressure), as measureover part of a reflectance cycle. (Excerpt from Wolthuis et. al).

Thus, by using this ratiometric technique the intraocular pressuremeasuring system of the present invention is insensitive to sourceintensity and coupling efficiency. In this regard, this type of opticalpressure sensor 10 has been coupled to a fiber optic/LED/dicroticmirror/photodiode system manufactured by Integra Neurosciences, SanDiego, Calif. to measure pressure. FIGS. 6 and 7 (excerpted fromWolthius et al.) demonstrate the linearity and reproducibility of themeasurements obtainable from this type of sensor 10.

Although FIGS. 1 and 2 show the optical sensor 10 positioned in theanterior chamber AC of the eye, it will be appreciated that this opticalsensor 10 may be positioned anywhere in the eye where intraocularpressure may be measured. For example, the sensor 10 may be positionedin the posterior chamber of the eye. Such positioning of the sensor 10within the posterior chamber of the eye may be accomplished by removingall or a portion of the vireous humor using known vitrectomy techniquesand then placing the sensor 10 (with or without an appropriatelyconfigured support 11) within the posterior chamber at a location wherelight may pass through the cornea, through the pupil and be reflectedfrom the reflective surface 22 of the diaphragm 20. In another example,in a patient who's native lens has been removed due to cataracts or someother pathology, a prosthetic lens may be implanted in place of thepreviously removed native lens and the sensor 10 may be attached thatprosthetic lens implant. Also, it is to be appreciated that variousother types of supports 11 may be used. In some instances, the support11 may be a structure which functions only to support the sensor 10. Inother instances, the support may perform some secondary function isaddition to holding of the sensor 10. For example, in embodiments wherethe support 11 is a phakic intraocular lens, the phakic intraocular lensmay be constructed to provide some refractive vision correction inaddition to holding of the sensor 10. In other instances, in patientswho suffer from glaucoma, a shunt may be surgically implanted tofacilitate drainage of aqueous humor and resultant lowering ofintraocular pressure. Such shunts are typically tubular and one end ofthe shunt typically protrudes into the anterior chamber AC of the eye.Thus, the optical sensor 10 may be attached to such a shunt (e.g., tothe portion of the shunt that resides in the anterior chamber of theeye) such that the shunt will perform the dual function of drainingaqueous humor and holding the sensor 10 at a desired location within theeye.

EXAMPLE 2 Intraocular Analyte Determining System

FIGS. 8, 9A and 9B show a system for quantitative or qualitativedetermination of an analyte within the eye of a human or veterinarypatient. This system comprises an optical analyte sensor 40 that isimplanted within the eye. This optical analyte sensor 40 may beconfigured for implantation as a stand alone device or may be attachedto a support 11A. In the particular embodiment shown, the support 11Acomprises an intraocular lens system that comprises an optic 12 a and ahaptic 14 a, of the same type as described hereabove in reference toFIG. 2.

The optical analyte sensor 40 is shown in detail in FIGS. 9A and 9B. Asshown, the optical analyte sensor 40 comprises a translucent body 46 (oran opaque body having a translucent window) having a hollow cavity 48formed at one end thereof. One or more walls of the cavity 48, or atleast a portion of one wall of the cavity 48, is/are formed of asemipermeable membrane 50 through which a particular analyte (e.g.,glucose or some other endogenous substance, a drug, a metabolite, atoxin, etc) will pass. In the embodiment shown, a flexible diaphragm 42having a reflective surface 44 is mounted transversely within the cavity48. As the concentration of the analyte increases in the body fluidadjacent to the outer surface of the semipermeable membrane 50, theanalyte will diffuse through the semipermeable membrane 50 and into thecavity 48. Some quantity of water may also diffuse into the cavity 48along with the analyte. This results in an increase in pressure on thediaphragm 42 and will cause the diaphragm to move as shown in FIG. 9A.When the concentration of the analyte in the body fluid decreases,analyte (and possibly water) will diffuse out of the cavity 48, therebydecreasing the pressure on the diaphragm and causing the diaphragm 42 tomove in the opposite direction, as shown in FIG. 9B. It will beappreciated that as an alternative to positioning of the diaphragm 42within the cavity 48, the semipermeable membrane may either abut thepressure-sensitive interferometric cavity, or the membrane may itselfserve as the pressure-sensitive diaphragm of the inteterferometer. Theability to measure concentrations of analytes by these optical analytesensors 40 may be quite sensitive.

In some embodiments of this invention, chemicals that either react orinteract with specific analytes may be placed in the cavity 48. Changessuch as altered optical spectroscopic (direct sensing) or volumetricproperties (pressure transduction) may then be detected. In this casethe semipermeable membrane could be fairly non-selective. The membrane50 may be any suitable type of membrane that will allow measurement ofthe analyte(s) of interest. Biomembranes permeable to specific analytes(e.g. glucose) have been developed (e.g., UPE Membrane, Millipore,Bedford, Mass.). Selectively permeable membranes may be used fordifferent analytes, including glucose.

The concentration of the analyte is read using a light source 30,receiver 32 and processor (e.g., a spectrometer) 34 in the same manneras described hereabove with respect to the optical pressure sensor 10.

EXAMPLE 3 Combined System for Measuring Intraocular Pressure and AnalyteConcentration

FIG. 10 shows another embodiment of the present invention wherein boththe optical pressure sensor 10 and optical analyte sensor 40 areattached to a common support 11B that comprises an intraocular lensassembly implanted in the anterior chamber Ac of a patient's eye. Thesupport includes an optic 12 b and haptic 14 c which may be the same asthose described above with respect to FIG. 2.

In this embodiment wherein the optical pressure sensor 10 and theoptical analyte sensor 40 are used in combination, a single light source30 or separate light sources 30, may be used to cast light on thereflective surfaces 22 and 44 of the optical pressure sensor diaphragm20 and the optical analyte sensor diaphragm 40, respectively. Inembodiments where a single light source is used, such single lightsource may be adjustable to vary the direction, wavelength and/or othercharacteristics of the of the light beam that emanates from the lightsource, thereby facilitating its use for both applications. Also, asingle receiver/processor 34 or separate receiver processors 34. May beused to receive and process the light reflected from the reflectivesurfaces 22 and 22. In embodiments where a single receiver/processor isused, such single receiver/processor may be adjustable to vary thedirection from which the reflected light is received and/or theparticular characteristic(s) of the reflected light that are processedby the processor,

Although the invention has been described above with respect to certainembodiments and examples, it is to be appreciated that such embodimentsand examples are non-limiting and are not purported to define allembodiments and examples of the invention. Indeed, those of skill in theart will recognize that various modifications may be made to theabove-described embodiments and examples without departing from theintended spirit and scope of the invention and it is intended that allsuch modifications be included within the scope of the following claims.

What is claimed is:
 1. An intraoccular pressure sensing systemcomprising: an inplantable optical pressure sensor sized forimplantation within the eye, said optical pressure sensor comprising anoptical reflecting element which varies relative to changes inintraoccular pressure and a window through which light will pass; alight source useable to pass light through the cornea of the eye andthrough the window of the pressure sensor such that the light willstrike the optical reflecting element; a receiver/processor whichreceives light which has reflected from the optical reflecting elementand processes such reflected light so as to obtain an indication ofintraoccular pressure.
 2. A system according to claim 1 wherein theimplantable pressure sensor is attached to a support that holds theimplantable pressure sensor in a substantially fixed position within theeye.
 3. A system according to claim 2 wherein the support comprises ahaptic.
 4. A system according to claim 2 wherein the support comprises ahaptic and and optic.
 5. A system according to claim 4 wherein thesensor is mounted on the haptic.
 6. A system according to claim 4wherein the sensor is mounted on the optic.
 7. A system according toclaim 2 wherein the support is configured to hold the implantablepressure sensor substantially within the anterior chamber of the eye. 8.A system according to claim 2 wherein the support is configured to holdthe implantable pressure sensor substantially within the posteriorchamber of the eye.
 9. A system according to claim 2 wherein the supportcomprises a shunt apparatus that may be implanted in the eye to decreasethe intraocular pressure of that eye.
 10. A system according to claim 2wherein the support comprises a prosthetic lens that has been implantedin place of the patient's native ophthalmic lens.
 11. A system accordingto claim 1 wherein the implantable pressure sensor is attached to aphakic intraocular lens.
 12. A system according to claim 11 wherein thephakic intraocular lens is constructed to perform a vision correctingfunction as well as the function of holding the implantable pressuresensor in a substantially fixed position.
 13. A system according toclaim 2 wherein the support holds the implantable pressure sensor withinthe eye such that light may pass from the light source, through thecornea of the eye and onto the optical reflecting element.
 14. A systemaccording to claim 1 wherein the implantable optic pressure sensorcomprises a Fabry-Perot interferometer pressure sensor.
 15. A systemaccording to claim 1 wherein the light source is a visible light source.16. A system according to claim 1 wherein the light source is an LEDlight source.
 17. A system according to claim 1 wherein thereceiver/processor unit comprises a spectrometer.